1. Field of the Invention
The present invention relates to a locking mechanism for a push-push switch.
2. Description of Background Art
A push-push switch is generally known which comprises a heart-shaped cam groove and may repeatedly be opened or closed by pressing a knob. For example, a push-push switch disclosed in Japanese Utility Model Publication No. Sho. 61-44352 comprises a heart-shaped cam groove provided on the side of a contact holder adapted to be moved by a knob, and a lock pin supported on the side of a switch case and arranged to engage the contact holder, the lock pin being biased in the direction of engagement with the heart-shaped cam groove by a return spring of the contact holder.
In the foregoing example of a conventional structure, because the heart-shaped cam groove is provided on the side of the movable contact holder, the latter must be large. Thus, there is a drawback that the contact holder needs an extra space and a switch assembly may also be large.
Also when the lock pin is biased by means of the return spring of the contact holder for engagement with the heart-shaped cam groove, the number of parts may be reduced, but there is the possibility that the heart-shaped cam groove may be deformed by a hard abutment with the lock pin because a considerably strong spring is used therein. On the contrary, if a weak spring is used, it becomes unstable to operate the contact holder. It is therefore quite difficult to maintain the well-balanced strength of the spring.